Determination of the effect of thickness reduction ratio, die angle, and coefficient of friction on residual stresses in ironing process: an analysis using computer simulation

Ironing is a part of the group of metal forming processes, the process of reducing the thickness of the wall of a cup-shaped product. External load required to process metal forming, can cause residual stress. Residual stress can be beneficial or detrimental depending on the function of the product, the magnitude, and direction of the residual stress. Residual stress can act as an additional load on a given load. Residual stress can affect product quality, namely: dimensional accuracy, surface roughness, and mechanical properties. The speed of the ironing process is strongly influenced by the mechanical properties of the cup material, Thickness Reduction Ratio (TRR), and press tool design. The ironing process has a limited TRR value and if it is exceeded it results in product damage. Various studies on ironing were carried out to obtain an optimal process. In this research, stress analysis was carried out using the ANSYS software modeling simulation to obtain the occurring residual stress during the ironing process. The analysis was carried out by varying the TRR from 20 % to 30 %, the die angle from 25° to 30°, and the coefficient of friction from 0.05 to 0.15. Furthermore, processing and analysis of the stress analysis data are carried out to obtain the most dominant variables affecting the residual stress and the variable value that produces the lowest residual stress. Stress analysis was carried out on AA1100 aluminum cups with an outer diameter of 37 mm, a height of 20 mm, and a wall thickness of 2 mm. The results show that TRR and coefficient of friction are the most dominant variables affecting residual stress, while die angle has no significant effect. The lowest residual stress occurs at TRR 30 % and coefficient of friction 0.15

Download Full-text

Residual Stress Characterization of Electroformed Ni-Base Alloy for μ-Gear Mold

Materials Science Forum ◽

10.4028/www.scientific.net/msf.773-774.640 ◽

2013 ◽

Vol 773-774 ◽

pp. 640-645

Author(s):

Seong Ho Son ◽

Sung Cheol Park ◽

Hyeong Mi Kim ◽

Won Sik Lee ◽

Hong Kee Lee

Keyword(s):

Residual Stress ◽

Pulse Current ◽

Base Alloy ◽

Dimensional Accuracy ◽

Powder Injection ◽

Outer Diameter ◽

Fe Content ◽

Injection Molded ◽

Fe Alloys

The micro gear molds for powder injection molding were fabricated by electroforming process of Ni-Fe alloys. The residual stress at interface between electrodeposit and substrate was important for micro electroforming. Addition of 6 g/L saccharin lowered residual stress from 466.3 MPa up to 32.8 MPa and increase of Fe content resulted in increase of residual stress. Electrodeposition by pulse current decreased residual stress in deposit although Fe content was increased. These results reveal clearly that decrease of residual stress due to pulse current is larger than increase of residual stress due to higher Fe content. The micro electroformed gear molds with 550 μm and 2,525 μm in outer diameter and 400 μm in height were fabricated by micro electroforming and 316L feedstock was injection-molded into micro molds. As a result, it is suggested strongly that micro electroforming is very useful process to manufacture micro mold with high dimensional accuracy for micro PIM.

Download Full-text

Investigation on the Characteristic of Residual Stress Distribution in the Dissimilar Metal Welds of a Small Bore Penetration Nozzle by Three-Dimensional Finite Element Analysis

ASME 2011 Pressure Vessels and Piping Conference: Volume 6, Parts A and B ◽

10.1115/pvp2011-57157 ◽

2011 ◽

Author(s):

Joong-Hyun Seo ◽

Jong-Sung Kim

Keyword(s):

Residual Stress ◽

Finite Element Analysis ◽

Finite Element ◽

Stress Analysis ◽

Three Dimensional ◽

Outer Diameter ◽

Element Analysis ◽

Dimensional Finite Element ◽

Residual Stress Analysis ◽

Three Dimensional Finite Element

In this study, three-dimensional finite element residual stress analysis of a small bore penetration nozzle was performed using the commercial finite element program, ABAQUS. Comparing with the real PWSCC (primary water stress corrosion crack) history, it is identified that the finite element analysis is valid in the viewpoint of PWSCC initiation and growth. Parametric finite element residual stress analysis was systematically implemented in order to investigate effect of the geometric variables including nozzle outer diameter/thickness, buttering thickness, angle between central axes of head & nozzle, etc. on the residual stresses. As a result of the parametric analysis, it is found that effects of the nozzle outer diameter and the angle between central axes of head & nozzle on the maximum residual stress generation location and magnitude are significant while effects of the head thickness, the buttering thickness, the weld depth, and the nozzle thickness to outer diameter are insignificant.

Download Full-text

Sheet Metal Forming Limit Prediction with Maximum Thickness Reduction Ratio

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.314-316.999 ◽

2011 ◽

Vol 314-316 ◽

pp. 999-1004

Author(s):

Jie Shi Chen ◽

Jun Chen

Keyword(s):

Numerical Simulation ◽

Sheet Metal ◽

Sheet Metal Forming ◽

Metal Forming ◽

Strain Path ◽

Reduction Ratio ◽

Thickness Reduction ◽

Forming Limit ◽

Forming Process ◽

Maximum Thickness

Maximum thickness reduction ratio is used to predict sheet metal forming limit in the numerical simulation of forming process. The maximum thickness reduction ratio under different stain path is not a constant for the same material. The effect of strain path and strain hardening exponent on forming limit is considered. The relationship between the maximum thickness reduction ratio that the material can obtained and the strain path between tensile to equi-biaxial is established. The parameter in the criterion can be determined by tensile experiment combined with numerical simulation of the same forming process. Then the limit strains under other linear strain paths between tensile to equi-biaxial can be determined by the criterion combined with numerical simulation of corresponding forming process. Forming limits of three kinds of sheet metals are predicted with the modified maximum thickness reduction ratio criterion. Good agreement is achieved between the predicted data and the experimental data.

Download Full-text

Design and Experimental Verification during Extrusion of Square Sections from Round Billets through Curved Dies

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.491.249 ◽

2011 ◽

Vol 491 ◽

pp. 249-256 ◽

Cited By ~ 1

Author(s):

Akshaya Kumar Rout ◽

Kali Pada Maity ◽

Manoja Kumar Parida

Keyword(s):

Mechanical Properties ◽

Theoretical Model ◽

Metal Forming ◽

Dimensional Accuracy ◽

Extrusion Process ◽

Uniform Microstructure ◽

Dead Metal Zone ◽

Extruded Product ◽

Cad Models ◽

Die Profile

Extrusion is one of the widely used metal forming processes. The extrusion process is carried out conventionally using a shear faced die, but shear faced dies have many practical problems such as a dead metal zone, more redundant work. In the present investigation, the evolution of uniform microstructure in extruded product with improved mechanical properties for quality products to get dimensional accuracy. A mathematically contoured non-linear converging die has been designed for extrusion of square section from round billet. CAD models of die profile have also been developed. The experiments have been conducted to verify the proposed theoretical model. The extrusion test rigs have been fabricated to carry out extrusion through mathematically contoured dies.

Download Full-text